Higher speed computers come with a cost—higher electrical consumption. For a small number of home PCs this extra power may be negligible when compared to the cost of running other electrical appliances in a household. However, in data center applications, where thousands or tens of thousands of microprocessors may be operated, electrical power consumption becomes important.
In addition, the power consumed by a microprocessor is transformed into heat. A pair of microprocessors mounted on a single motherboard can draw 200-400 watts or more of power. If that power draw is multiplied by several thousand (or tens of thousands) to account for the computers in a data center, the potential for heat generation can be appreciated. Thus, not only must a data center operator pay for electricity to operate the computers, it must also pay to cool the computers. The cost of removing heat may be a major cost of operating large data centers.
A typical approach to removing heat in a data center uses air conditioning, e.g., cold air is blown through the room containing the computers. For example, a current common practice is to construct a data center on a raised floor, and use a computer room air conditioner to force cold air through ducts below the floor and up through holes in the floor beneath or between the server racks. The cold air flows over the microprocessors and is heated, and the heated air can be drawn through ceiling ducts back to the computer room air conditioner.